Pub Date : 2022-05-01DOI: 10.1080/15567265.2022.2070561
M. Sahebi, A. Azimian
ABSTRACT In this study, using the molecular dynamics simulation method, three systems for fluid pumping at the nanoscale have been proposed based on the thermo-osmotic mechanism. These pumps work by applying a symmetric temperature gradient along the wall of a nanopore, which is asymmetric in shape or material. The three systems are a composite nanotube, a conical nanotube, and a composite conical nanopore. The simulation results show that, in all of the proposed systems, the fluid can be pumped continuously by means of heat energy and without using any external force or moving component. The physical mechanisms of the flow in these pumps are clarified using the principles of the thermo-osmotic phenomenon. The simulations show the geometry of the pump and the fluid-solid interaction strength play an important role in determining the pumping strength in all systems. It is shown that a composite conical nanopump compared to other proposed systems has a better performance in fluid pumping.
{"title":"Nanoscale fluid pumping using a symmetric temperature gradient: a molecular dynamics study","authors":"M. Sahebi, A. Azimian","doi":"10.1080/15567265.2022.2070561","DOIUrl":"https://doi.org/10.1080/15567265.2022.2070561","url":null,"abstract":"ABSTRACT In this study, using the molecular dynamics simulation method, three systems for fluid pumping at the nanoscale have been proposed based on the thermo-osmotic mechanism. These pumps work by applying a symmetric temperature gradient along the wall of a nanopore, which is asymmetric in shape or material. The three systems are a composite nanotube, a conical nanotube, and a composite conical nanopore. The simulation results show that, in all of the proposed systems, the fluid can be pumped continuously by means of heat energy and without using any external force or moving component. The physical mechanisms of the flow in these pumps are clarified using the principles of the thermo-osmotic phenomenon. The simulations show the geometry of the pump and the fluid-solid interaction strength play an important role in determining the pumping strength in all systems. It is shown that a composite conical nanopump compared to other proposed systems has a better performance in fluid pumping.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"26 1","pages":"84 - 94"},"PeriodicalIF":4.1,"publicationDate":"2022-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47869860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-02DOI: 10.1080/15567265.2022.2066585
S. M. Hatam-Lee, F. Jabbari, A. Rajabpour
ABSTRACT Silica coating on a gold nanoparticle can improve its thermal application in cancer thermotherapy. In this paper, the interfacial thermal conductance between gold and silica is calculated utilizing classical non-equilibrium molecular dynamics. It is revealed that the results of molecular dynamics are different from what has been predicted by the conventional diffuse mismatch model. Furthermore, the interfacial thermal conductance between amorphous SiO2 and gold is approximately twice that of crystalline silica, which is explained by calculating the vibrational density of state mismatches. The interfacial thermal conductance variations in terms of van der Waals interaction strength between gold and silica are also investigated. It is revealed that the conductance increases by about 30% by increasing the simulation temperature from 300 to 700 K. The results of this paper can be useful in nanofluid systems, in addition to the application of silica-coated gold nanoparticles in cancer thermal therapy.
{"title":"Interfacial thermal conductance between gold and SiO2: A molecular dynamics study","authors":"S. M. Hatam-Lee, F. Jabbari, A. Rajabpour","doi":"10.1080/15567265.2022.2066585","DOIUrl":"https://doi.org/10.1080/15567265.2022.2066585","url":null,"abstract":"ABSTRACT Silica coating on a gold nanoparticle can improve its thermal application in cancer thermotherapy. In this paper, the interfacial thermal conductance between gold and silica is calculated utilizing classical non-equilibrium molecular dynamics. It is revealed that the results of molecular dynamics are different from what has been predicted by the conventional diffuse mismatch model. Furthermore, the interfacial thermal conductance between amorphous SiO2 and gold is approximately twice that of crystalline silica, which is explained by calculating the vibrational density of state mismatches. The interfacial thermal conductance variations in terms of van der Waals interaction strength between gold and silica are also investigated. It is revealed that the conductance increases by about 30% by increasing the simulation temperature from 300 to 700 K. The results of this paper can be useful in nanofluid systems, in addition to the application of silica-coated gold nanoparticles in cancer thermal therapy.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"26 1","pages":"40 - 51"},"PeriodicalIF":4.1,"publicationDate":"2022-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46832610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-02DOI: 10.1080/15567265.2022.2069615
Umit Nazli Temel, Ferhat Kilinc, Serkan Coşkun
ABSTRACT This experimental study focused on the comparison of thermal protection performances of macro and/or nano enhanced organic PCM in a representative battery pack from low to high discharge rates. The macro/nano enhanced RT-44 provides the desired battery thermal protection requirements in terms of criteria such as maximum temperature and maximum temperature difference restriction and uniform temperature distribution throughout the battery pack. It increases the effective battery thermal protection time by 117%-32% depending on the discharge rates. While PCM thermal protection provides a more homogeneous temperature distribution throughout the battery pack, nano and/or macro enhanced one provides it throughout the cell. The macro enhancement essentially makes a major contribution to shortening the cooling time for the next use.
{"title":"Thermal Protection Performances of the Macro and/or Nano Enhanced PCM in a Representative Battery Pack","authors":"Umit Nazli Temel, Ferhat Kilinc, Serkan Coşkun","doi":"10.1080/15567265.2022.2069615","DOIUrl":"https://doi.org/10.1080/15567265.2022.2069615","url":null,"abstract":"ABSTRACT This experimental study focused on the comparison of thermal protection performances of macro and/or nano enhanced organic PCM in a representative battery pack from low to high discharge rates. The macro/nano enhanced RT-44 provides the desired battery thermal protection requirements in terms of criteria such as maximum temperature and maximum temperature difference restriction and uniform temperature distribution throughout the battery pack. It increases the effective battery thermal protection time by 117%-32% depending on the discharge rates. While PCM thermal protection provides a more homogeneous temperature distribution throughout the battery pack, nano and/or macro enhanced one provides it throughout the cell. The macro enhancement essentially makes a major contribution to shortening the cooling time for the next use.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"26 1","pages":"52 - 66"},"PeriodicalIF":4.1,"publicationDate":"2022-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45042519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-02DOI: 10.1080/15567265.2022.2028044
Shivanand H. Nannuri, Sana Adnan, Subash C K, S. C, S. George
ABSTRACT The influence of Mn2+ ion concentration (x = 0–20 mol%) as well as the role of thermal-annealing temperature (400–600°C) on the structural as well as luminescence properties of NaYF4:Yb, Er (Y: 78-x%, Yb: 20%, Er: 2%) microcrystals prepared via a coprecipitation method is investigated. The cubic phase of the as-prepared NaYF4:Yb, Er (Y: 78%, Yb: 20%, Er: 2%) was found to remain intact upon the addition of the Mn2+ ions, but the thermal-annealing elucidates that the phase of the sample depends upon the annealing temperature as well as the Mn2+ ion concentration. Among the Mn2+ ion co-doped samples, 3 mol% doped samples dominant to have a maximum positive influence on the upconversion luminescence of the sample, and a further increase in concentration leads to the concentration-induced quenching of the upconversion luminescence. Moreover, the enhancement factor of green ( ), as well as red ( ) emission, depend upon the annealing temperature, with a maximum enhancement factor of 5 and 3.12 times for the sample annealed at 400°C, 8.6 and 7.25 times for the sample annealed at 500°C, and 6 and 4 times for the sample annealed at 600°C, as compared to Mn2+ ion undoped samples. The maximum emission strength for the green as well as red is observed for the sample annealed at 600°C and co-doped with 3 mol Mn2+ ions. The laser power-dependent study on all the samples shows that the upconversion process is a multi-photon process, predominantly a two-photon process. Graphical abstract
{"title":"Thermal Annealing and Doping Induced Tailoring of Phase and Upconversion Luminescence of NaYF4:Yb Er Microcrystals","authors":"Shivanand H. Nannuri, Sana Adnan, Subash C K, S. C, S. George","doi":"10.1080/15567265.2022.2028044","DOIUrl":"https://doi.org/10.1080/15567265.2022.2028044","url":null,"abstract":"ABSTRACT The influence of Mn2+ ion concentration (x = 0–20 mol%) as well as the role of thermal-annealing temperature (400–600°C) on the structural as well as luminescence properties of NaYF4:Yb, Er (Y: 78-x%, Yb: 20%, Er: 2%) microcrystals prepared via a coprecipitation method is investigated. The cubic phase of the as-prepared NaYF4:Yb, Er (Y: 78%, Yb: 20%, Er: 2%) was found to remain intact upon the addition of the Mn2+ ions, but the thermal-annealing elucidates that the phase of the sample depends upon the annealing temperature as well as the Mn2+ ion concentration. Among the Mn2+ ion co-doped samples, 3 mol% doped samples dominant to have a maximum positive influence on the upconversion luminescence of the sample, and a further increase in concentration leads to the concentration-induced quenching of the upconversion luminescence. Moreover, the enhancement factor of green ( ), as well as red ( ) emission, depend upon the annealing temperature, with a maximum enhancement factor of 5 and 3.12 times for the sample annealed at 400°C, 8.6 and 7.25 times for the sample annealed at 500°C, and 6 and 4 times for the sample annealed at 600°C, as compared to Mn2+ ion undoped samples. The maximum emission strength for the green as well as red is observed for the sample annealed at 600°C and co-doped with 3 mol Mn2+ ions. The laser power-dependent study on all the samples shows that the upconversion process is a multi-photon process, predominantly a two-photon process. Graphical abstract","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"26 1","pages":"1 - 16"},"PeriodicalIF":4.1,"publicationDate":"2022-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48912026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-02DOI: 10.1080/15567265.2022.2070562
U. Aziz, M. Nadeem, Feng Xin, M. Kiliç, A. Ullah
ABSTRACT The slug flow in a superhydrophobic microchannel with a T-junction was studied computationally. The continuous phase passed through the main channel while the dispersed phase 1 1. was introduced through the side channel. The volume of fluid (VOF) was employed to track the interface to study the dynamics of slug flow. First, a mesh independence study was carried out to select the optimum mesh by comparison of CFD results with experimental data. The developed model of microchannel was used to study slug flow heat transfer enhancement for micro cooling of electronic chips. The constant heat flux was applied on the walls of the microchannels and the axial wall temperature profile was noted. Upon quantification of heat transfer augmentation in terms of wall temperature reduction, Nusselt number and heat transfer coefficient enhancement, it was noted that slug flow performed much better vis-à-vis single-phase flows at similar conditions.
{"title":"Evaluation of Thermal Hydraulic Characteristics of a Two Phase Superhydrophobic Microfluidic Device using Volume of Fluid Method","authors":"U. Aziz, M. Nadeem, Feng Xin, M. Kiliç, A. Ullah","doi":"10.1080/15567265.2022.2070562","DOIUrl":"https://doi.org/10.1080/15567265.2022.2070562","url":null,"abstract":"ABSTRACT The slug flow in a superhydrophobic microchannel with a T-junction was studied computationally. The continuous phase passed through the main channel while the dispersed phase 1 1. was introduced through the side channel. The volume of fluid (VOF) was employed to track the interface to study the dynamics of slug flow. First, a mesh independence study was carried out to select the optimum mesh by comparison of CFD results with experimental data. The developed model of microchannel was used to study slug flow heat transfer enhancement for micro cooling of electronic chips. The constant heat flux was applied on the walls of the microchannels and the axial wall temperature profile was noted. Upon quantification of heat transfer augmentation in terms of wall temperature reduction, Nusselt number and heat transfer coefficient enhancement, it was noted that slug flow performed much better vis-à-vis single-phase flows at similar conditions.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"26 1","pages":"67 - 82"},"PeriodicalIF":4.1,"publicationDate":"2022-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48695717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-27DOI: 10.1080/15567265.2021.2019861
Can Ji, Zhigang Liu, Mingming Lv, Ji-chao Li
ABSTRACT Micro pin fin heat sink is a very attractive cooling technique for high power density microelectronics. Optimization of its cooling performance requires insightful understanding on fundamental physics of flow inside it, especially around a single pin fin. In the present study, an experimental investigation on flow past an isolated low aspect ratio (height-to-diameter ratio) pin fin embedded in a microchannel is conducted using Micro-PIV. The flow field and vorticity distribution at different channel heights under various Reynolds numbers are obtained. Endwall effect is found to play an important role in flow past the pin fin in the microchannel, and the critical Reynolds numbers are larger than that at the conventional scale. Vorticity concentrations are formed on both sides of the pin fin along the shear layer and intensify with the increase in Reynolds number. Flow fields and vorticity distributions at different heights exhibit different characteristics, especially at higher Reynolds numbers, indicating three-dimensionalities of the flow. Viscous resistance of the endwalls leads to lower overall velocity, smaller extent of the recirculation zone and weaker vorticity in flow layer closer to the top and bottom channel walls. Pressure drop and flow resistance characteristics in the microdevice is analyzed. The effect of aspect ratio of the pin fin on the wake flow is also studied, and the results show that three-dimensionalities increase but critical Reynolds numbers decrease with larger aspect ratios. A comparison with flow across micro pin fin arrays is conducted and differences are observed in velocity field and wake flow features.
{"title":"Experimental Investigation on Flow Past an Isolated Micro Pin Fin Embedded in a Microchannel","authors":"Can Ji, Zhigang Liu, Mingming Lv, Ji-chao Li","doi":"10.1080/15567265.2021.2019861","DOIUrl":"https://doi.org/10.1080/15567265.2021.2019861","url":null,"abstract":"ABSTRACT Micro pin fin heat sink is a very attractive cooling technique for high power density microelectronics. Optimization of its cooling performance requires insightful understanding on fundamental physics of flow inside it, especially around a single pin fin. In the present study, an experimental investigation on flow past an isolated low aspect ratio (height-to-diameter ratio) pin fin embedded in a microchannel is conducted using Micro-PIV. The flow field and vorticity distribution at different channel heights under various Reynolds numbers are obtained. Endwall effect is found to play an important role in flow past the pin fin in the microchannel, and the critical Reynolds numbers are larger than that at the conventional scale. Vorticity concentrations are formed on both sides of the pin fin along the shear layer and intensify with the increase in Reynolds number. Flow fields and vorticity distributions at different heights exhibit different characteristics, especially at higher Reynolds numbers, indicating three-dimensionalities of the flow. Viscous resistance of the endwalls leads to lower overall velocity, smaller extent of the recirculation zone and weaker vorticity in flow layer closer to the top and bottom channel walls. Pressure drop and flow resistance characteristics in the microdevice is analyzed. The effect of aspect ratio of the pin fin on the wake flow is also studied, and the results show that three-dimensionalities increase but critical Reynolds numbers decrease with larger aspect ratios. A comparison with flow across micro pin fin arrays is conducted and differences are observed in velocity field and wake flow features.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"26 1","pages":"17 - 39"},"PeriodicalIF":4.1,"publicationDate":"2021-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46507866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-02DOI: 10.1080/15567265.2021.2011993
Sardar S. Abdullah, S. Hashemi, N. A. Hussein, R. Nazemnezhad
ABSTRACT Nonlinear torsional vibration of nanorods embedded in an elastic medium under three-dimensional thermal stresses is investigated in this study. The scale effect is introduced to the equation of motion using the nonlocal theory. The nanorods are under the effect of a three-dimensional thermal environment. The elastic medium is modeled by infinite rotational springs around the nanorod. Galerkin’s and He’s variational methods are used to solve the differential equation of motion and obtain torsional frequencies. An uncertainty analysis is done to show the effect of the uncertain parameters on the frequencies. The frequency sensitivities are obtained to demonstrate the frequency sensitivities to uncertain parameters. Effect of temperature changes, elastic medium stiffness, vibration amplitude, nonlocal scale coefficient, and nanorod length and diameter on the nonlinear torsional frequencies are investigated. The effect of temperature on the frequencies is dependent on the values of elastic medium stiffness, vibration amplitude, and nanorod length and diameter.
{"title":"Three-Dimensional Thermal Stress Effects on Nonlinear Torsional Vibration of Carbon Nanotubes Embedded in an Elastic Medium","authors":"Sardar S. Abdullah, S. Hashemi, N. A. Hussein, R. Nazemnezhad","doi":"10.1080/15567265.2021.2011993","DOIUrl":"https://doi.org/10.1080/15567265.2021.2011993","url":null,"abstract":"ABSTRACT Nonlinear torsional vibration of nanorods embedded in an elastic medium under three-dimensional thermal stresses is investigated in this study. The scale effect is introduced to the equation of motion using the nonlocal theory. The nanorods are under the effect of a three-dimensional thermal environment. The elastic medium is modeled by infinite rotational springs around the nanorod. Galerkin’s and He’s variational methods are used to solve the differential equation of motion and obtain torsional frequencies. An uncertainty analysis is done to show the effect of the uncertain parameters on the frequencies. The frequency sensitivities are obtained to demonstrate the frequency sensitivities to uncertain parameters. Effect of temperature changes, elastic medium stiffness, vibration amplitude, nonlocal scale coefficient, and nanorod length and diameter on the nonlinear torsional frequencies are investigated. The effect of temperature on the frequencies is dependent on the values of elastic medium stiffness, vibration amplitude, and nanorod length and diameter.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"25 1","pages":"179 - 206"},"PeriodicalIF":4.1,"publicationDate":"2021-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46112838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-30DOI: 10.1080/15567265.2021.1985022
S. Sobolev
ABSTRACT The trend toward miniaturization of electronic devices has increased the interest in nano scale heat transport, particularly, in laser-excited solids where electron–electron thermalization and electron-phonon coupling play a key role. Using a multi-temperature hyperbolic model, which takes into account the coupling between initially non-thermalized electrons and different phonon branches, we obtain a hierarchy of heat conduction equations for the electron temperature, which arises due to multi-length and time scales nature of coupling between different excitations. The hierarchy predicts that the ultrashort laser pulse induces a multi-front temperature wave propagating into the bulk of the material, which includes various heat transport regimes, ranging from the ballistic motion of the initially non-thermalized electrons propagating on the shortest time scale without interaction with the lattice as a temperature discontinuity, to the continuous wave-like temperature fronts arising on the intermediate time scale due to coupling between various excitations, and eventually to the classical Fourier transport on the longest time scale. The model is expected to be useful for modeling heat wave propagation phenomena in heterostructures and metamaterials.
{"title":"Local Nonequilibrium Electron Transport in Metals after Femtosecond Laser Pulses: A Multi-Temperature Hyperbolic Model","authors":"S. Sobolev","doi":"10.1080/15567265.2021.1985022","DOIUrl":"https://doi.org/10.1080/15567265.2021.1985022","url":null,"abstract":"ABSTRACT The trend toward miniaturization of electronic devices has increased the interest in nano scale heat transport, particularly, in laser-excited solids where electron–electron thermalization and electron-phonon coupling play a key role. Using a multi-temperature hyperbolic model, which takes into account the coupling between initially non-thermalized electrons and different phonon branches, we obtain a hierarchy of heat conduction equations for the electron temperature, which arises due to multi-length and time scales nature of coupling between different excitations. The hierarchy predicts that the ultrashort laser pulse induces a multi-front temperature wave propagating into the bulk of the material, which includes various heat transport regimes, ranging from the ballistic motion of the initially non-thermalized electrons propagating on the shortest time scale without interaction with the lattice as a temperature discontinuity, to the continuous wave-like temperature fronts arising on the intermediate time scale due to coupling between various excitations, and eventually to the classical Fourier transport on the longest time scale. The model is expected to be useful for modeling heat wave propagation phenomena in heterostructures and metamaterials.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"25 1","pages":"153 - 165"},"PeriodicalIF":4.1,"publicationDate":"2021-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47005421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-02DOI: 10.1080/15567265.2021.1958960
Jonathan Sullivan, Ziqi Yu, Jaeho Lee
ABSTRACT While anti-reflective properties of pyramid texture are widely used, their use for thermal radiation control has received relatively little attention and the understanding of geometric parameters for design optimization is not well established. Here we use finite-difference time-domain simulations in conjunction with an algorithm to optimize thermal characteristics of micropyramid-textured metallic, ceramic, and polymer materials. Our simulations indicate that the pyramid height-to-base ratio is an effective parameter in developing an engineered thermal response. For nickel, the micropyramids with 2–4 height-to-base ratios over 0.5–4 µm base spans provide near-perfect absorption in 300–2500 nm wavelengths. The electric field analysis shows the optical properties are driven by the effects of localized resonance and field confinement. Our thermal cost function-based optimization has led to micropyramid texture that can have a significant impact on heating or cooling such as the solar absorption increase in nickel from 337 to 982 W/m2, the thermal emission increase in alumina from 106 to 170 W/m2, and the thermal emission increase in PDMS from 160 to 172 W/m2. This work not only provides the understanding of micropyramid properties for thermal radiation control but also presents an algorithmic process that could be used for efficient optical-thermal optimization of geometries beyond micropyramids.
{"title":"Optical Analysis and Optimization of Micropyramid Texture for Thermal Radiation Control","authors":"Jonathan Sullivan, Ziqi Yu, Jaeho Lee","doi":"10.1080/15567265.2021.1958960","DOIUrl":"https://doi.org/10.1080/15567265.2021.1958960","url":null,"abstract":"ABSTRACT While anti-reflective properties of pyramid texture are widely used, their use for thermal radiation control has received relatively little attention and the understanding of geometric parameters for design optimization is not well established. Here we use finite-difference time-domain simulations in conjunction with an algorithm to optimize thermal characteristics of micropyramid-textured metallic, ceramic, and polymer materials. Our simulations indicate that the pyramid height-to-base ratio is an effective parameter in developing an engineered thermal response. For nickel, the micropyramids with 2–4 height-to-base ratios over 0.5–4 µm base spans provide near-perfect absorption in 300–2500 nm wavelengths. The electric field analysis shows the optical properties are driven by the effects of localized resonance and field confinement. Our thermal cost function-based optimization has led to micropyramid texture that can have a significant impact on heating or cooling such as the solar absorption increase in nickel from 337 to 982 W/m2, the thermal emission increase in alumina from 106 to 170 W/m2, and the thermal emission increase in PDMS from 160 to 172 W/m2. This work not only provides the understanding of micropyramid properties for thermal radiation control but also presents an algorithmic process that could be used for efficient optical-thermal optimization of geometries beyond micropyramids.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"25 1","pages":"137 - 152"},"PeriodicalIF":4.1,"publicationDate":"2021-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2021.1958960","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47078568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-03DOI: 10.1080/15567265.2021.1912865
Shouyuan Huang, Yijie Chen, Zhe Luo, Xianfan Xu
ABSTRACT Micro-Raman thermometry is an effective method for measuring thermal conductivity of thin films. It features noncontact and nondestructive probing and convenience of sample preparation. However, there is a concern of its accuracy when using the Raman peak shift as the temperature transducer since it responds to both temperature and strain upon optical heating. In this work, a series of detailed experiments are carried out to evaluate contributions to Raman signals from temperature only vs. from thermomechanical strain. It is shown that using proper calibration, contributions to Raman signals from temperature only and from thermomechanical strain can be decoupled and thermal conductivity can be evaluated correctly. These procedures are then applied to bismuth telluride thin films to illustrate measurement of thin film thermal conductivity.
{"title":"Temperature and Strain Effects in Micro-Raman Thermometry for Measuring In-Plane Thermal Conductivity of Thin Films","authors":"Shouyuan Huang, Yijie Chen, Zhe Luo, Xianfan Xu","doi":"10.1080/15567265.2021.1912865","DOIUrl":"https://doi.org/10.1080/15567265.2021.1912865","url":null,"abstract":"ABSTRACT Micro-Raman thermometry is an effective method for measuring thermal conductivity of thin films. It features noncontact and nondestructive probing and convenience of sample preparation. However, there is a concern of its accuracy when using the Raman peak shift as the temperature transducer since it responds to both temperature and strain upon optical heating. In this work, a series of detailed experiments are carried out to evaluate contributions to Raman signals from temperature only vs. from thermomechanical strain. It is shown that using proper calibration, contributions to Raman signals from temperature only and from thermomechanical strain can be decoupled and thermal conductivity can be evaluated correctly. These procedures are then applied to bismuth telluride thin films to illustrate measurement of thin film thermal conductivity.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"25 1","pages":"91 - 100"},"PeriodicalIF":4.1,"publicationDate":"2021-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2021.1912865","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43362393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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